P30 Update on land surface component used in operational WRF-based RAP and HRRR

Smirnova, Tanya, John M. Brown, Stan Benjamin, Ming Hu, National Oceanic and Atmospheric Administration/Global Systems Division, Boulder, CO

RUC Land-Surface Model (LSM), option 3 in the Weather Research and Forecast (WRF) model, is used as a land surface component in the operational Rapid Refresh (RAP) over North America domain and in the High-Resolution Rapid Refresh (HRRR) over CONUS and Alaska domains. It also became available in NASA Land Information System (LIS) 7.2r public release that came out on 6 May 2017. Work has been started to implement RUC LSM in the Next Generation Global Prediction System (NGGPS) as part of the RAP/HRRR physics suite. The RUC LSM performance has been evaluated for almost two decades within the real-time operational weather prediction systems focused on storm-scale predictions for severe weather and safer aviation. In the recent couple of years it has been more and more extensively utilized by the WRF community in different parts of the world, including Arctic regions, and for different applications. Valuable feedback from the National Weather Prediction forecast offices and the WRF community has motivated further advances towards better representation of processes in snow-covered regions. The new treatment has been implemented for grid cells partially covered with snow. It considers snow-covered and non-snow-covered portions of a grid cell independently, and independently determined surface fluxes are aggregated to feed back into the surface-layer scheme at the end of each time step. This new "mosaic" approach removes the constraint of keeping skin temperature of partially covered with snow grid cells at or below the freezing point, and helps to reduce cold biases in these regions. It also helps to get improvements in the evolution of cycled in the model snow cover together with the new semi-empirical formulations for the density of frozen precipitation depending on hydrometeor type and surface temperature. The enhancements to the snow model are getting validated through participation in the new Earth System Model-Snow Model Intercomparison Project (ESM-SnowMIP), are being tested in the experimental verisons of RAP/HRRR at ESRL, and will be implemented in the next operational versions of RAP and HRRR at NCEP. Other enhancements include use of real-time, daily updated 4-km VIIRS Green Vegetation Fraction (VIIRS-GVF) to initialize vegetation state in RAP and HRRR. The comparison to currently used MODIS climatology shows some improvements in surface predictions in the areas with substantial deviation from the climatological mean. Results from these comparisons will be presented at the meeting.